Air Conditioning - Outside fan does not turn off

Hi,
I searched the forums and did not find an answer so I'd appreciate your help with my problem. It seems that even if the A/C condensor is off the outside fan continues to run. In fact, if I switch my t-stat to the "off" position so it is neither heating or cooling the outside fan still continues to run on my A/C, although no air is coming through the vents. The only way I can shut the fan off is to throw the breaker.

What things should I do or check to see if I can get it functioning properly again?
Thanks!
Erik

I would think either control circuitry or a relay. However, as you have turned it to off then I would say it is the relay that controls the fan. It may have stuck in the on position.

However, you'd have to troubleshot that fan and relay circuit to be sure.

eb

I've never worked with A/C units before. Will the relays be obvious if I were to take the cover off the outside unit? How difficult would you think it would be to set the switch to the off position? Is this something that can be done manually or is it more of an electric/computerized switch?

Is the fan running at full normal speed or at a reduced speed when it should be off?

Is the fan running at full normal speed or at a reduced speed when it should be off?

Normal speed.

I actually just went out there and took off the cover from the A/C and it's all pretty basic looking. There is simpy a small coil and then attached to it is a series of screws with wires attached. There are two wires coming out (a black and red) that lead into a quick release that the fan wires are clipped in to, so I'm thinking that if the fan just needs to be replaced that it would be a fairly easy procedure. Now I'm just wondering if the switch that operates the fan is within the fan unit or if it's within the mechanics of the compressor/somewhere else.

Where would I even get a new fan if I did want to try replacing it?

It also seems that the condensor is running along with the fan because there is frost built up on the fat wire outside even though the cool air is not being circulated through the house.

If both fan and compressor are running then you may have a Contactor problem. We will need a good volt meter and some electrical checking skill do we have that?

Yes, I've got both a volt meter and electrical checking skill.

Excellent now what we need to determine is if the 24 volts that pulls the contactor in is being cut off and then the contactor stays engaged. There are two small wires that carry voltage to the contactor magnetic coil. There will be one attached to each side of your contactor. Check between the two with the t-stat calling for cooling the reading should be approx 24 volts and the contactor should be pulled in. Now set the t-stat to the off position you should not have voltage between the two small coil wires and the contactor should pop out. If you still have 24 volts to the coil with the t-stat set to off replace the t-stat. If the t-stat properly cuts off the voltage and the contactor does not pop out then replace the contactor as the contacts are pitted and it is welding itself together and cannot release.

I just went and probed around the contactor and in doing so I got the contactor to pop out and all is right with the A/C again. Short term the problem is fixed, but long term I'll need to get a new contactor and replace it so this doesn't happen again. I've been able to turn the A/C on and off without a problem though since I "unstuck" the "button".

Thanks for your help... I really learned a lot.

yes a stuck closed contactor is always the first thing you look for when your outside unit runs when it is not being called, for less than 25 bucks you out to be able to cure this problem

I've read that the contactor often times has a residual charge left in it even after the power ie shut off, so for future reference, how do I make sure that contactor is fully decharged before working with it?

Thanks again,
Erik

Sorry it took me so long to get back to you but it is hot and I am in the air conditioning business.
You are talking about the capacitor not the contactor the capacitor is a device to assist in running a PSC electric motor against resistance and it can be charged with electricity and if that electricity has nowhere to go it can be discharged into you if you happen to touch it this does not not happen nearly as much as it is rumored to have happened and the only way is if the power is on to the capacitor and there is no load for it to go to meaning the wires to the motor would have to be broken (corroded or disconnected) If you want to make sure this does not happen to you you can take an insulated screwdriver and touch the shaft to one of the terminals on top of the capacitor to some metal that is grounded to the unit and this will discharge any stored voltage